A former Palmerston North mayoral candidate has been sentenced to community work after racking up his fourth conviction for assaulting children.

Ross Easton Barber, 50, winked and smiled at his supporters in the Palmerston North District Court yesterday as he was sentenced to 100 hours' community work for assaulting a boy. He was also ordered to pay the child $1000 in emotional harm reparation.

Barber was found guilty of the charge after a judge-alone trial earlier this year.

Barber, who stood for mayor of Palmerston North at last year's election, filmed the assault, which took place on his piggery just outside the city.

On a date between October 2006 and October 2008, the boy, who was between 8 and 9 years old at the time, was at the piggery. The two had an argument, and the boy became agitated.

Barber grabbed his video camera and filmed what happened next - something he later told police was done to show the boy how bad his behaviour was.

The boy walked out of an office on the piggery and Barber followed, calling him a "cry baby" and telling him to "smile for the camera".

He tried to throw some things at Barber before walking onto the driveway, where he either tripped or was pushed over.

Barber then held the child down by putting one foot on his chest and holding one arm, as the boy cried and coughed.

He maintained he provoked the boy to try to get him to talk instead of reacting violently.

But at the sentencing, Judge Les Atkins said the behaviour was clearly an assault.

"This was someone dealing with a child in a way which involved some physical force which amounted to an assault, but also a huge degree of mental cruelty.

‘This was a child that was being provoked into a worse state of distress by the way you were dealing with him.

"The cruelty of your actions was simply appalling."

The video of the assault had made police officers feel distressed, which the judge said was a natural reaction.

"Anybody who would not be distressed when viewing that would lack any feeling whatsoever."

While Barber had three previous convictions for assaulting children, this attack happened before the other three.

That meant the charge had to be treated like a first offence.

The judge said if it happened after the other attacks, Barber would be heading to prison.

Defence lawyer Mike Andrews said Barber would rather pay more emotional harm reparation than get significant community work hours, as they would get in the way of him running his piggery.